1. Field of the Invention
This invention relates to the field of display processors for computer displays.
2. Background Art
As part of computer based information systems, it is often desired to provide a means for controlling the display of data on a output device such as a printer or screen, (for example, a Cathode Ray Tube (CRT)). In order to make a computer system operate more efficiently, a plurality of displays are superimposed on the screen at one time. Each of these individual displays is referred to as a "window" and typically each window represents different programs which are being executed by the computer. These windows often overlap onto the display screen, with only the topmost window being entirely visible. Although certain portions of the underlying windows are not visible, the data found in these portions is preserved in memory.
In the past, displays utilizing windows have used a number of window buffers, with each buffer containing data for a single window. Prior to display, the contents of the window buffers are mapped into a bit map frame buffer. The contents of this frame buffer are then read, typically in raster fashion, to provide the visual display. The order in which the window buffers are mapped into the bit map frame buffer depends on the order of the windows on the ultimate display.
The above-described method of generating window displays has the disadvantage of requiring a bit-block transfer of data in the frame buffer of the altered area each time a window is updated or a window position on the display screen is changed. This is a time consuming process and requires additional memory space to implement. Further, the data in those portions of windows underlying other windows must be stored in window frame buffers, adding to the time and memory requirements of such a window map system.
Therefore it is an object of the present invention to provide a display management system which allows the display of a plurality of overlapping windows with a minimum of storage updates and memory requirements.
It is another object of the present invention to provide a display management system which does not require a bit map frame buffer.
It is yet another object of the present invention to provide a display management system which allows for efficient display of plurality of windows on a computer display screen.